1. Field of the Invention
The present invention relates to a toothbrush which pumps dentifrice material from a replaceable cartridge to the brush head. In particular, the invention provides means which increases the pumping efficiency and which facilitates cleaning the brush head after it is used.
2. Description of the Prior Art
There are a variety of toothbrushes which store and dispense dentifrice material from the handle of the brush. One type of brush dispenses the dentifrice material at the base of the brush head where the bristles are attached, such as that described in U.S. Pat. No. 4,068,974. Another type dispenses dentifrice material directly onto the top of the brush surface. U.S. Pat. No. 4,787,765 describes this type of brush. Most brushes store dentifrice material directly in a reservoir in the brush handle as typified by the brush shown in U.S. Pat. No. 4,269,207. Other brushes store the dentifrice material in a replaceable cartridge which is positioned in the reservoir. U.S. Pat. No. 4,116,570, as well as previously referenced U.S. Pat. Nos. 4,269,207, 4,068,974 and 4,787,765, describe brushes having this feature. Some of the cartridge toothbrushes contain a follower disc which advances in the cartridge as material is pumped therefrom and which serves as a seal to prevent backflow of material. This feature is described in U.S. Pat. Nos. 4,269,207 and 4,787,765. The prior art also includes toothbrushes that store dentifrice material in their handles which have detachable brush heads. Exemplary patents in this regard include U.S. Pat. Nos. 4,269,207 and 4,332,497.
The foregoing discussion illustrates some of the improvements which have been made in the design, structure and operation of toothbrushes that store dentifrice material in their handles. However, the adhesive, paste-like consistency of many dentifrice materials, has resulted in difficulties in consistently providing a smooth, void free flow of material and in cleansing residual material from the brush head after its use. The most widely used dentifrice material, commonly referred to as "toothpaste", is a gel which has an adhesive nature. While this characteristic allows it to remain firm on brush surfaces during periods of use, it also causes it to adhere to the bristles after use as well as to other parts within the toothbrush that are in the flow path. Efficiently cleaning the residual material from the brush is a significant problem in a bottom fed brush because substantial material remains at the base of the brush head, interposed between bristles and the brush surface. Also, residual material remains in the opening at the base of the brush where material is fed to the brush. If material is not thoroughly cleaned from the opening, the material becomes dried and eventually clogs the opening.
Replaceable cartridges having follower discs provide an advantageous alternative for storing dentifrice material directly in a toothbrush reservoir. However, continuous pumping by the user after the cartridge is empty, may cause a very severe problem. A certain quantity of dentifrice material still can be pumped from the pump chamber, channels and other areas outside of the spent cartridge, but this causes the formation of voids in these places. Such over pumping may result in a breakdown of the vacuum force that is required for efficient pump operation and a consequent failure to pump any dentifrice material from a new cartridge.
One way to avoid over-pumping involves the user's monitoring of the position of the follower disc through a viewing port in the handle. A viewing port as described in U.S. Pat. No. 4,787,765 allows the user to determine when the cartridge is nearly empty by observing the position of the follower disc. However, this approach does not ensure a failure-free operation of the toothbrush since the user may neglect to observe the position of the follower disc through the viewing port and to refrain from further pumping when the cartridge is empty. It is therefore desireable to have a self-locking mechanism built into the toothbrush to prevent the user from further pumping when the cartridge has reached a near empty state.
Another problem originates when a spent cartridge is being removed and is caused by the adhesiveness of the dentifrice material. As the spent cartridge is removed, some residual material sticks to the follower disc and material remains attached to the pump mechanism within the brush handle. In the configurations of a replaceable cartridge and a pumping piston as described in U.S. Pat. No. 4,787,765, dentifrice material adheres to the follower disc during removal of a spent cartridge. The material adhering to the follower disc is removed from part of the material in the pump chamber. Similar to the previously described over-pumping situation, the quantity of dentifrice material that is pulled out of the pump chamber by its adherence to the follower disc, is not replaced when a new cartridge is inserted. Consequently, upon insertion of the new cartridge, voids are created which may deteriorate pumping efficiency and result in a complete pump failure.
There is a need for a dentifrice dispensing toothbrush which efficiently overcomes problems that are caused by over-pumping and by the adhesive consistency of paste-like dentifrice materials. More specifically, there is a need for a cartridge toothbrush which pumps and prevents further pumping when its cartridge is empty and retains sufficient amount of material within its handle as the spent cartridge is removed to prevent the formation of voids when a new cartridge is inserted. There is also a need for a dentifrice dispensing toothbrush that has a brush head that can be conveniently and thoroughly cleaned of material that adheres to the bristles and clogs the feed opening after each use.
It is therefore an object of this invention to provide a toothbrush with a replaceable cartridge containing dentifrice material which ensures a continuous flow stream of dentifrice material when it is pumped therethrough.
It is a further object of the invention to provide a toothbrush for storing dentifrice material which can be easily and efficiently cleaned after each use.